1. Field of the Invention
The present invention relates to a piezoelectric material, a method of manufacturing the piezoelectric material, and a piezoelectric device using the material. More specifically, the present invention relates to a perovskite-type orientation piezoelectric material and a method of manufacturing thereof, in particular, to a lead-free piezoelectric material.
2. Description of the Related Art
Piezoelectric devices are devices for converting electric energy into mechanical energy, i.e., a mechanical displacement, stress or vibration, or is a device for converting in the opposite direction. Piezoelectric devices are used for ultrasonic motors, ink jet heads, and the like.
Many piezoelectric materials which are used for piezoelectric devices are called PZT, and are oxides containing lead (Pb), zirconium (Zr), and titanium (Ti). Therefore, for addressing an environmental problem, a piezoelectric material containing no lead (lead-free piezoelectric material) is being developed.
As a promising lead-free piezoelectric material, there is known a material obtained by domain engineering after controlling orientation of BaTiO3, so that the piezoelectric property is improved (S. Wada, Japanese Journal of Applied Physics, Vol. 46, No. 10B, 2007, pp. 7039-7043). Domain engineering requires a polycrystal in (110) orientation of its micro-grains.
On the other hand, as a promising lead-free piezoelectric material having MPB composition similar to PZT, there is known xBi(Mg1/3Ti2/3)O3-(1-x)BaTi3 (0≦x≦1), which has been synthesized only as a thin-film single crystal (Japanese Patent Application Laid-Open No. 2008-98627). The thin-film single crystal has no grains in general, and therefore domain engineering is inapplicable to the same. From a viewpoint of charge balance, as a lead-free piezoelectric material having the same element structure, Bi(Mg1/2T1/2)O3-(1-x)BaTiO3 (0≦x≦1) (hereinafter, also referred to as “BMT-BT”, which also may be written with numerals indicating a composition ratio of BMT to BT) is rather stable, and it is preferred to obtain a BMT-BT bulk material.
However, a solid solution of Bi(Mg1/2Ti1/2)O3 and BaTiO3 has a disadvantage in that it is difficult to disperse the raw material powder sufficiently when they are mixed and sintered, and an undesired phase, which may be referred to as a “secondary” phase, other than perovskite may easily be formed. Therefore, it is difficult to obtain a bulk material. Thus, there has been no reported example of a bulk material of BMT-BT.